textproduct: Rapid City

KEY MESSAGES

- Isolated severe thunderstorms possible this afternoon/evening across portions of northeastern WY and southwestern SD. Main hazards will be large hail (1+" in diameter) and damaging wind gusts (60+ mph)

- Slight risk of severe thunderstorms Thursday afternoon/evening, mainly across northeastern WY

- Active pattern continues with chances for severe storms Friday and Saturday, though there is still some uncertainty in location and timing.

DISCUSSION

(This Afternoon Through Tuesday) Issued at 1149 AM MDT Wed Jun 24 2026

Upper air analysis depicts weak wave moving across northeastern WY into western SD. The disturbance has triggered the development of a few showers/storms over northeastern WY and the Black Hills. This activity should continue through the afternoon and evening hours as 500 mb speed max remains over the region. Bulk shear values of 40-50kt and modest instability of 500-1000 J/kg should contribute to a marginal severe threat across portions of northeastern WY into southwestern SD with the main hazards being large hail and damaging winds.

Near zonal flow pattern continues through Thursday with another shortwave moving across the Northern Plains by the afternoon/evening hours. Morning cloud cover may limit daytime heating and overall severe potential with 12z models showing ~500-1500 J/kg CAPE over the far western reaches of our CWA by 3 pm tomorrow afternoon. Most recent CAMs indicate a line of storms developing off the Big Horns tomorrow afternoon with initial storm development having the greatest severe potential (main hazards will be large hail and damaging winds). The line of storms will move eastward through the CWA as the evening progresses. While a few storms may become strong and we could see some severe caliber wind gusts as the line moves through, as of now not anticipating any widespread severe weather across western SD as the storms move through.

Longwave trough moves into the western US on Friday with zonal westerly flow over our neck of the woods transitioning to southwest flow. Southeasterly sfc flow will bring warm, moist air into the region with ML CAPE values rising to 2000 to 3000 J/kg across western SD by the late afternoon/evening hours. However weak upper level ridging and warm 750 mb temps contributing to a strong cap will likely keep the severe threat conditional for Friday.

Attention turns to severe potential on Saturday as a shortwave and attendant lee cyclone moves through the region. There's still some uncertainty as to the timing and location of the lee cyclone and where the greatest instability will be by the afternoon. So correspondingly, confidence is low in the exact location and timing of any severe weather risks for Saturday with the most likely area to see severe weather across portions of northwestern and north central SD.

AVIATION

(For the 18Z TAFS Through 18Z Thursday) Issued At 1053 AM MDT Wed Jun 24 2026

Mainly VFR conditions expected through 25/06z. Scattered showers/isolated thunderstorms will continue over northeastern WY/southwestern SD through this afternoon/early evening, mostly south of Interstate 90. Local MVFR conditions will occur with the heaviest showers. MVFR/local IFR CIGS will develop over northeastern WY/southwestern SD after 25/06z as moist southeast upslope flow occurs.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.